A grease for a slide contact has been used for a sliding switch and the like of a vehicle such as an automobiles and the like. The following properties are required of the grease in particular:
(i) It does not exert a harmful influence upon slide parts made of resins such as ABS, POM and the like. PA1 (ii) It is hard to deteriorate under arc heat generated at the time of switching the load-break. PA1 (iii) It does not change in quality at temperatures used for soldering a lead wire in a process for producing the switch. PA1 (iv) It has a pour point of less than -45.degree. C. and can be used at low temperatures.
However, there is no grease for the slide contact having all the aforesaid properties among the former greases which are prepared by blending various additives such as a thickener (e.g. soap such as lithium stearate, 12-hydroxy lithium stearate and the like), an anticorrosive, an antioxidant and the like with a mineral oil or a synthetic oil as a base oil.
For example, in the case of the grease which comprises lithium stearate as a thickener, said lithium salt hardens to a varnish like solid state after being heated to a soldering temperature higher than the dropping point of the grease and forms a hard, insulating film on the contact surfaces to which the grease is applied thus exerting a harmful influence upon the electric contact. In the case of the grease which comprises 12-hydroxy lithium stearate as a thickener, a carbonized product of the grease formed by arc heating brings about an insulating deterioration of the switch, although the insulating film is not formed at the soldering temperature.
Furthermore, in the case of the grease which comprises a clay mineral containing hydrated magnesium silicate, such as sepiolite and the like, as an anticorrosive, the grease does not satisfy all of the aforementioned requirements, although an excellent rust-resisting effect can be obtained (Japanese Patent Opening No. 115997/1986).